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Don't understand Spat error message

Spat
#1

Hello,

While trying to set positions of speakers in Spat, I got this error message : "spat5.pan~: [14:17:21.489] error occurred when processing “/speakers/aed 123.755 0.0 0.485918 114.306 0.0 0.653606 118.949 0.0 0.835343 129.177 0.0 0.942943 140.823 0.0 0.942943 151.051 0.0 0.835344 155.694 0.0 0.653606 146.361 0.0 0.485654 97.0296 0.0 0.310996 93.1511 0.0 0.692388 107.79 0.0 1.01025 125.705 0.0 1.1846 144.295 0.0 1.1846 162.21 0.0 1.01025 176.849 0.0 0.692389 172.97 0.0 0.310997 135.228 0.0 0.709941”. Reason: invalid loudspeaker setup for “angular” panning : the reference position (x=0,y=0,z=0) must be ‘inside’ the loudspeaker setup. "

What does “the reference position must be ‘inside’ the loudspeaker setup” mean ?

#2

Hello,

The reference position (x=y=z=0) is the center of the coordinate system, i.e. the “sweet spot”/listener position.
Most panning algorithms are designed for “surround” loudspeaker setups, where the listener/reference position is “inside” the loudspeakers (typically arranged as circle, square, dome, cube, etc.)

In your example, the listener is totally “outside” the speaker systems, and therefore the geometrical calculations used by the panning algorithms will fail.

Basically two options:

  1. use a distance-based panning algorithm instead (KNN or DBAP).
  2. translate all the loudspeakers so that they surround the listener position.
    However, option #2 will raise another issue: your setup exhibits multiple “concentric rings”, which is also prohibited by angle-based panning algorithms (“angular”, VBAP, etc.) Why ? Because these algorithms relie on basic geometrical calculations, simply taking into account the relative angle between source(s) and speaker(s). Therefore they cannot distinguish between loudspeaker #1 and #9, #2 and #10, #3 and #11, etc. because they have similar directions.

Also have a look at “spat5.tuto-vbap-1.maxpat”.

I hope this clarifies a bit. (these geometrical issues are not easy to explain with words…)

Best,
T.

#3

I wasn’t aware of this limitation of angle-panning algorithms. Thank you for the information @tcarpent.